It is taught in U.S. Pat. No. 3,577,398 that a mixture of piperylene and 2-methylbutene-2 polymerizes in the presence of a metal halide catalyst to form a series of hydrocarbon polymers which are very useful in a number of commercial applications requiring resinous materials.
One particular application is as components of industrial adhesives. For the pressure sensitive adhesives, for example, increasing the softening point of the resinous component improves the adhesive peel strength and elevated temperature response of the adhesive.
Conventional sources of piperylene mixtures used to produce these resinous hydrocarbon products are crude feed streams derived from steam cracked naphthas and catalytically cracked distillate streams containing large quantities of olefins in the C.sub.5 to C.sub.10 ranges (see U.S. Pat. Nos. 2,753,325 and 2,753,382). Streams generally have large amounts of other unsaturated hydrocarbons, particularly hydrocarbons containing from 4 to 6 carbon atoms. Representative examples of such hydrocarbons are 2-methylbutene-1, 3-methylbutene-1, pentene-1, pentene-2, and isoprene. According to U.S. Pat. No. 3,577,398 up to about 50 weight percent of said unsaturated hydrocarbons based on the weight of the piperylene 2-methylbutene-2 mixture can be present without deleteriously modifying the polymerized resin. The primary unsaturated hydrocarbons in these feed streams are pentene-1, 2-methylbutene-1, t-pentene-2, c-pentene-2, 3-methylbutene-1 and cyclopentene.
It is known that mono-olefin feedstocks can be usefully isomerized by double bond migration to convert 2-methylbutene-1 and/or 3-methylbutene-1 to 2-methylbutene-2 and pentene-1 to cis- and trans-pentene-2 (see U.S. Patents: Nos. 3,151,179; 3,268,617; 3,290,404; and 3,920,765).
It is desirable to obtain hydrocarbon resins with lower molecular weights but without detrimental loss of softening points in view of the better high temperature properties the higher softening point contributes in the end use formulations with other polymers.
It is therefore an object of this invention to provide a process for the polymerization of olefins obtained from a crude feed stream obtained from the cracking of petroleum fractions whereby hydrocarbon resins of lower molecular weight are obtained.